The battle was also the first to be fought largely by civilian volunteers rather than professional soldiers. These patriotic men became known as the “Pals” battalions, a term coined by Lord Derby, many of whom saw their first major action on the first day of the Somme offensive. Consequently the units sustained major losses – some 19,000 men died on the first day alone.

The events of the Somme had such an impact on those who survived that Britain saw a rising tide of psychiatric casualties and doctors began to consider psychological disorders as a branch of mainstream medicine for the first time.

During World War I, the overall level of psychiatric causalities mirrored that of physical casualties. The designated “signature injury” of the Great War was deemed to be “shell shock” by Captain Charles Myers in 1915. This blanket term was used to describe various manifestations that were affecting men at war, for example, fits, tremors and nightmares. Shell shock has a variety of causes and affected a range of those who witnessed the horrors of war: from determined regular soldiers who served on the frontline for extended periods of time, to individuals who just weren’t properly prepared for battle, having received minimal training before being thrown into the middle of it. Although not a medical term, shell shock should only be used when referring to World War I and the common man’s experience of it.

Today many of the symptoms associated with shell shock would be considered medically unexplained, however during 1915-1916 many soldiers were discharged from service because doctors just weren’t sure how to treat them. Such high discharge rates resulted in – particularly after the Somme – a crisis of manpower: the British Army was in desperate need to find a way to conserve their fighting strength.

The solution came in the form of “forward psychiatry” – later given the acronym “PIE”. First employed by the French, it was a method of treating reactions to combat stress with the aim of preventing long-term psychiatric illness. Casualty clearing stations were set up within close “proximity” (10-20 miles) of the front line allowing “immediacy” of treatment with the “expectancy” of a recovery. At the time it was claimed the PIE method saw 70% of soldiers return to the front within two weeks. However, research has since demonstrated that such outcome statistics were both inaccurate and misleading. Though the principles of forward psychiatry are still in place in current conflicts its heyday has now passed.

A modern day shell shock?

Though the casualty rates of more recent conflicts are relatively low compared to World War I, there seems to be an overlap between the symptoms associated with shell shock and mild traumatic brain injury (mTBI), the claimed signature injury of the Iraq and Afghanistan conflicts. The similarities centre around exposure to blast force on the battlefield: 100 years ago soldiers were exposed to exploding artillery shells but more recent campaigns have seen soldiers exposed to improvised explosive devices (IEDs).

Asked to describe what it is like to endure such an explosion, Gary Joynson, who served in the British Army on operations in Iraq and Afghanistan said: “The shock waves pass through you so fast, and your whole body is left feeling like you have just belly flopped into a one inch paddling pool.”

Brain effects

Blast waves from IEDs expose the body to huge amounts of kinetic energy, propagating as a shock wave passing through the skull and essentially bruising the brain. Recent research suggested that there may be a unique pattern of physical damage to the human brain after blast exposure. This distinctive scarring occurs in areas of the brain where tissues of different densities intersect. Researchers identified brain regions (for example, the amygdala, anterior cingulate cortex and orbitofrontal cortex) whose function had been altered due to blast exposure.

The brain regions identified to be affected by blast scarring are the same regions whose function, if disrupted, will result in the unexplained symptoms soldiers experienced during World War I as well as some of those currently ascribed to PTSD. Considering this, we may now need to contemplate the possibility that not all PTSD symptoms are purely psychological – some may be the result of physical damage to the brain. These initial findings require further investigation, however, and should be interpreted with caution – though they do provide some insight into the possible underlying cause of the inexplicable manifestations presented by soldiers 100 years ago.

It is also still unclear at what level of blast pressure damage to the brain occurs. Though new technology developed to record the pressure and acceleration experienced by soldiers could have the answer. A “black box” will undoubtedly inform current and further research in this field, and could guide efforts to reduce blast pressure exposure, as well as inform treatment interventions for those who continue to suffer from the invisible wounds sustained during conflict.

War is as it has always been, a dirty business. Living in austere conditions for extended periods of time is not uncommon and certainly not for the risk adverse. There is a stark difference between the pre-deployment training the “Pals” Battalions received, compared with our highly trained military force today, but preparing individuals for the emotionally challenging brutality of war is still difficult to achieve. However, 100 years after the Battle of the Somme, we may of finally solved the mystery behind some of the life altering psychological conditions experienced by those who fought for their country.